\typeout{Exercise and Answer macros} 
\typeout{Charles Wells cfw2@po.cwru.edu}
\typeout{24 February 1994}

% Copyright 1994 by Charles Frederick Wells.
% May be freely redistributed, provided that the files ans.sty,
% ansdoc.tex and onceexam.tex are distributed together and are not
% changed.

\makeatletter
% Counters for exercise and subexercise numbers
\newcounter{exercounter}
\newcounter{subexercounter}[exercounter]
% % \renewcommand{\thesubexercounter}{\subexerstyle{subexercounter}}
\newif\ifsols
\newif\ifanswerson
\newif\ifanswer
\newif\ifsubanswer
% Used to determine if the current exercise or subexercise
% has an answer


\def\exerbody{%
\setcounter{exercounter}{0}%
\ifanswerson\answerfalse\subanswerfalse\@wrheader\fi%
\ifsols\@wrsolheader\fi}
\newcommand{\exes}[1]{\exersection{#1}\exerbody}
% You can comment out the forms you don't want:
\newcommand{\exercises}{\exes{Ejercicios}}
\newcommand{\exercise}{\exes{Ejercicio}}
\newcommand{\problems}{\exes{Problemas}}
\newcommand{\extraproblems}{\exes{Extra Credit Problems}}
\newcommand{\samplequestions}{\exes{Sample Test Questions}}

% Amount of vertical space between exercises.
% It would be better to have this space depend on the
% type size.  In hindsight, I think each exercise section
% should be a specially created LaTeX list environment.
% But that's for the next revision!
\newskip\exerskipamount
\exerskipamount=6pt plus 1 pt 
\newcommand{\medgap}{\par\vskip\exerskipamount\noindent}

% \answermark is the symbol that marks questions with answers. 
% Put another symbol here in place of \bullet if you wish.  The
% spacing will take care of itself.  I hope.
\newcommand\answermark{\mbox{$^\bullet$}}


% The following commands set the numbering style for exercises and
% subexercises.  See page 92 of LaTeX book for other
% possibilities.
\def\exerstyle{\arabic}
\def\subexerstyle{\alph}

% The quantities below control the spacing after the problem number
% before the problem starts.  If you change \exerspace all the
% others should change automatically.  The idea is that all the
% problems start with the same indentation and the answer and hard
% symbols are stuck between without affecting the indentation.
% \newdimen{\hardback}
\newdimen{\answerspace}
\newdimen{\exerspace}
\newdimen{\tempdim}
\newdimen{\labeldim}
\settowidth{\labeldim}{\bf5}
\setlength{\exerspace}{\parindent}
\advance\exerspace by -\labeldim
\setlength{\answerspace}{\exerspace}
\settowidth{\tempdim}{\answermark}
\advance\answerspace by -\tempdim

% \@pns is the style of the problem number.  It is set to
% boldface.  Changing \@pns will change the styles of all the
% problem numbers and subproblem letters in both the exercise
% sections and the answer sections.  If you don't want them all
% the same you will have to search the file and change them by
% hand.  
\def\@pns{\bf}

% The following commands head exercises and subexercises.  (See
% ansdoc.tex for a more complete explanation.)  
\newcommand{\exer}{%
\ifnum\c@exercounter>0
\pagebreak[2]\else\nopagebreak\fi\medgap% 
\ifanswerson\ifanswer\noanserror\fi\answerfalse% 
\ifsubanswer\nosubanserror\fi\subanswerfalse\fi
\refstepcounter{exercounter}\setcounter{subexercounter}{0}% 
\@pns\exerstyle{exercounter}.\hspace{\exerspace}\rm}

% \exhead is a header for a set of exercises
\newcommand{\exhead}[1]{\ifnum\c@exercounter>0
\pagebreak[3]\else\nopagebreak\fi
\par\bigskip\noindent{\fbox{%
\advance\textwidth by -1em\parbox{\textwidth}{#1}}}}

% The two lines below produce a version of exhead that does
% not enclose the header in a box.  I changed to the boxed
% version when I noticed that a substantial number of students
% overlooked the header.
% \newcommand{\exhead}{\ifnum\c@exercounter>0
% \pagebreak[3]\else\nopagebreak\fi\par\bigskip\noindent}


\newcommand{\@ssa}% "offset subanswer"
{\phantom{\bf\exerstyle{exercounter}.\ }%
\bf\subexerstyle{subexercounter}}

\newcommand{\exera}{\ifnum\c@exercounter>0
\pagebreak[2]\else\nopagebreak\fi\medgap% 
\ifanswerson\ifanswer\noanserror\fi% 
\ifsubanswer\nosubanserror\fi\subanswerfalse\answertrue\fi
\refstepcounter{exercounter}\setcounter{subexercounter}{0}% 
\@pns\exerstyle{exercounter}.\answermark\hspace{\answerspace}\rm}

\def\eexer{\ifanswerson\ifanswer\noanserror\fi% 
\ifsubanswer\nosubanserror\fi\pagebreak[3]\@wrtail\fi%
\ifsols\@wrsoltail\fi}

\newcommand{\subexer}{\ifanswerson% 
\ifsubanswer\nosubanserror\fi\subanswerfalse\fi% 
\refstepcounter{subexercounter}% 
\nopagebreak[1]\par\noindent\@ssa.\hspace{\exerspace}\rm}

\newcommand{\subexera}{\ifanswerson% 
\ifsubanswer\nosubanserror\fi\answerfalse\subanswertrue\fi% 
\refstepcounter{subexercounter}% 
\nopagebreak[1]\par\noindent\@ssa.%
\answermark\hspace{\answerspace}\rm}

\newcommand{\immsubexer}{\ifanswerson% 
\ifsubanswer\nosubanserror\fi\subanswerfalse\fi% 
\refstepcounter{subexercounter}
\hspace{-\labeldim}\@pns\subexerstyle{subexercounter}.%
\hspace{\exerspace}\rm} 

\newcommand{\immsubexera}{\ifanswerson% 
\ifsubanswer\nosubanserror\fi\answerfalse\subanswertrue\fi% 
\refstepcounter{subexercounter}% 
\hspace{-\labeldim}\@pns\subexerstyle{subexercounter}.%
\answermark\hspace{\answerspace}\rm}

%%The following places the word "(#1)" in boldface after the
% exercise number. 
% I use it to mark exercises "hard", "requires Mathematica",
% etc.
\def\annot#1{\hspace{-\answerspace}{{\bf (#1)}}}

% These are the error messages for problems marked with the
% answermark that don't have answers and vice versa.
\newcommand\anserror{
\typeout{Warning:}
\typeout{Exercise \exerstyle{exercounter} has an answer but is not % 
marked}}
\newcommand\noanserror{
\typeout{Warning:}
\typeout{Exercise \exerstyle{exercounter} has no answer}}
\newcommand\nosubanserror{
\typeout{Warning:} 
\typeout{Exercise \exerstyle{exercounter}.%
\subexerstyle{subexercounter} % 
has no answer}}
\newcommand\subanserror{
\typeout{Warning:}
\typeout{Exercise \exerstyle{exercounter}.%
\subexerstyle{subexercounter} % 
has an answer but is not marked}}

% Following is a modification of the makeindex code.
% It defines the various answer macros that write appropriate
% headers to the answer file.  The answer file has the same name
% as the main file, with the extension ".ans".
% The stuff concerning rightmark etc. control the running heads in
% the answer section.  They won't appear unless you put
% \pagestyle{headings} in the preamble.
% The line in @wrheader beginning \string\ansection* controls what
% is printed before the answers to each section.
% The line saying \typeout controls the message on the screen.
\def\makeanswers{\answersontrue\if@filesw \newwrite\answerfile
  \immediate\openout\answerfile=\jobname.ans%
%makeanswers continues...
  \def\answer{\ifanswer\else\anserror\fi\answerfalse\par
\putinans{\string\antwort[\exerstyle{exercounter}]}\copytoblankline}%
%makeanswers continues...
  \def\subanswer{\ifsubanswer\else\subanserror\fi\subanswerfalse\par
      \ifnum\value{subexercounter}=1
    \putinans{\string\immsubantwort[\exerstyle{exercounter}]%
[\subexerstyle{subexercounter}]}\else 
    \putinans{\string\subantwort[%\string\phantom%
\exerstyle{exercounter}]%
[\subexerstyle{subexercounter}]}\fi
      \copytoblankline}%
%makeanswers continues...
  \def\immsubanswer{\subanswerfalse\par
  \putinans{\string\immsubantwort[\exerstyle{exercounter}]%
[\subexerstyle{subexercounter}]}% 
      \copytoblankline}%
   \typeout{Writing answer file \jobname.ans }\fi}% END \makeanswers

% The command \makesolutions below produces a second file of
% answers for the problems that aren't marked as having answers!
% By putting \dosolutions at the very end of the printout you can
% have a booklet of "answers to problems not answered in the
% text."
\def\makesolutions{\solstrue\if@filesw \newwrite\solutionfile
\newwrite\solutionfile
  \immediate\openout\solutionfile=\jobname.sol%
  \def\solution{\par
    \putinsol%
     {\string\antwort[\exerstyle{exercounter}]}%
     \copysoltoblankline\@esphack}%
  \def\subsolution{\par
      \ifnum\value{subexercounter}=1
    \putinsol{\string\immsubantwort[\exerstyle{exercounter}]%
[\subexerstyle{subexercounter}]}\else 
    \putinans{\string\subantwort[%\string\phantom%
{\exerstyle{exercounter}}]%
[\subexerstyle{subexercounter}]}\fi
      \copysoltoblankline}%
  \def\immsubsolution{\par
  \putinsol{\string\immsubantwort[\exerstyle{exercounter}]%
[\subexerstyle{subexercounter}]}% 
      \copysoltoblankline}%
   \typeout{Writing solutions file \jobname.sol}\fi}% END 


%\def\skiplf{\catcode`\^^J=9} 

% The following is by D. Knuth
% It reads a line up to a CR then writes it to file #1
% If it comes to a blank line it quits
% DON'T MESS WITH THIS CODE.  EVEN BREAKING OR COMBINING THE 
% LINES CAN MESS IT UP.
\def\copytoblankline{\begingroup\setupcopy\copyans}
\def\copysoltoblankline{\begingroup\setupcopy\copysol}
   \def\setupcopy{\def\do##1{\catcode`##1=\other}\dospecials
   \catcode`\|=\other \obeylines}
   {\obeylines \gdef\copyans#1
     {\def\next{#1}% 
      \ifx\next\empty\let\next=\endgroup% 
      \else\immediate\write\answerfile{\next} \let\next=\copyans\fi\next}}
   {\obeylines \gdef\copysol#1
     {\def\next{#1}% 
      \ifx\next\empty\let\next=\endgroup% 
      \else\immediate\write\solutionfile{\next} \let\next=\copysol\fi\next}}

% The following modification of copytoblankline is used 
% when answers are turned off
\def\throwaway{\begingroup\setupcopy\killans}
   {\obeylines \gdef\killans#1
     {\def\next{#1}% 
      \ifx\next\empty\let\next=\endgroup % 
      \else\let\next=\killans\fi\next}}

\chardef\other=12 

% The following commands take effect if \makeanswers is not 
% in preamble
% They are intended to do nothing
\def\@wrheader{\relax}
\def\@wrtail{\relax}
\def\@wrsolheader{\relax}
\def\@wrsoltail{\relax}
\def\answer{\throwaway}
\def\solution{\throwaway}
\def\subanswer{\throwaway}
\def\immsubanswer{\throwaway}



\answersonfalse
\solsfalse

% The words containing "antwort" format the answers in the
% answer file.

\def\ant{\@startsection
 {paragraph}{4}{\z@}{-6pt plus -2pt minus -1pt}{-1em plus
-.2em}{\normalsize\@pns}}


\def\antwort[#1]{\ant{#1.}} %%Note the period
% \def\subantwort[#1][#2]{\par\noindent\@pns#1\phantom{.}\ \ #2.\ \rm}
\def\subantwort[#1][#2]{\pagebreak[1]%
\medgap\@pns\phantom{#1.}\ \ #2.\ \rm}
\def\immsubantwort[#1][#2]{\pagebreak[2]\medgap\@pns#1.\ \ #2.\ \rm} 


% Here are some commands used repeatedly in \makeanswers and in
% the option commands \artsec, \bkchap, etc.
\def\putinans{\immediate\write\answerfile}
\def\putinsol{\immediate\write\solutionfile}
\def\putbreak{\string\pagebreak[3]\string\medbreak\noindent}

% This command is called by doanswers and can be used to customize
% the answer section.  For example, if you want the answers in
% small type, you could put "\def\@therstuff{\small}" in the
% preamble.
\def\@therstuff{\relax}

\def\do@nswers[#1]{
\ifanswerson\putinans{\string\par}
\immediate\closeout\answerfile% \fi
\@therstuff
\def\rightmark{\expandafter\@rightmark\botmark}
\def\leftmark{\expandafter\@leftmark\firstmark}\fi
\answersonfalse % minor kludge because answerfile is closed
\anshead
\input{#1.ans}
\eject}
 
% The following command should be put at place in the book where the
% answers go, e.g. after the bibliography and before the index.
% "Answers to selected exercises" heads the whole section.
% Answers to each section are headed by "Section #.#".  
% That is controlled by \@wrheader (above).
\def\doanswers{\@ifnextchar [{\do@nswers}{\do@nswers[\jobname]}}

\def\dos@ls[#1]{
\immediate\write\solutionfile{\string\par}
\immediate\closeout\solutionfile
\@therstuff
\setcounter{page}{1}
\def\rightmark{\expandafter\@rightmark\botmark}
\def\leftmark{\expandafter\@leftmark\firstmark}
\raggedbottom% In case not used earlier
\solhead
\input{#1.sol}
\eject}

% The command \dosolutions produces a booklet of answers to
% questions not answered in the text (provided you write the
% answers!)  It could be put at the end of the .tex file after
% resetting the page number.
\def\dosolutions{\@ifnextchar [{\dos@ls}{\dos@ls[\jobname]}}

% The following commands allow ans.sty to be used with book.sty or
% article.sty, with various arrangements of the exercises.

% Use this command in your preamble if you are using article style
% and have (at most) one section of exercises per section.
\def\artsec{%
  \def\exersection{\subsection}%
  \def\ansection{\section}%
  \def\anshead{%
    \section*{Answers to selected exercises}\label{ansec}
    \sectionmark{}}
  \def\solhead{%
    \noindent\section*{Soluciones para los ejercicios\protect\\ 
not answered in text}%
    \sectionmark{}}
  \def\@wrheader{\begingroup
      \xdef\@gtempa{%
\putinans{\string\ansection*{Secci\'on \thesection}\string\nopagebreak}
 \putinans{\string\typeout{Answers to Section \thesection}}
 \putinans{\string\markboth{Answers for Section \thesection}
{Answers for Section \thesection\string\enskip}}}
        \@gtempa\endgroup}%
   \def\@wrsolheader{\begingroup
      \xdef\@gtempa{%
 \putinsol{\string\ansection*{Secci\'on \thesection}\string\nopagebreak}
 \putinsol{\string\typeout{Soluciones de la secci\'on \thesection}}
 \putinsol{\string\markboth{Soluciones para la secci\'on \thesection}
{Soluciones para la secci\'on \thesection\string\enskip}}}
        \@gtempa\endgroup}%
   \def\@wrtail{\xdef\@gtempa{%
 \putinans{\string\markboth{Answers for Section \thesection}
{Answers for Section \thesection\string\enskip}}
  \putinans{\putbreak}}
       \@gtempa}
   \def\@wrsoltail{
\xdef\@gtempa{\putinsol{\string\markboth{Soluciones para la secci\'on
   \thesection}
{Soluciones para la secci\'on \thesection\string\enskip}}
    \putinsol{\string\pagebreak[3]\string\medbreak\noindent}}
       \@gtempa}}% end \artsec

% Use this command if you are using bookstyle and have at most one
% set of exercises per chapter.
\def\bkchap{%
  \def\exersection{\section}%
  \def\anstochap{\section}%
  \def\anshead{%
    \addcontentsline{toc}{part}{Answers to selected problems} 
    \chapter*{Answers to selected problems}\label{ansec}
    \chaptermark{}}
  \def\solhead{%
    \chapter*{Solutions to problems\protect\\ 
     not answered in text}
    \chaptermark{}}
   \def\@wrheader{\begingroup
      \xdef\@gtempa{%
 \putinans{\string\anstochap*{Capítulo \thechapter}\string\nopagebreak}
 \putinans{\string\typeout{Answers to Chapter \thechapter}}
  \putinans{\string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}
%       \putinans{%
% % The following causes the string "Solutions for Chapter n"
% % to be added IN THE FORMAT OF A SECTION ENTRY in the t.o.c
%  \string\addcontentsline{toc}{section}{\string\protect
%  \string\numberline{0}{Solutions for Chapter \thechapter}}}
}
        \@gtempa\endgroup}%
   \def\@wrsolheader{\begingroup
      \xdef\@gtempa%
 {\putinsol{\string\anstochap*{Capítulo \thechapter}\string\nopagebreak}
 \putinsol{\string\typeout{Soluciones para el Capítulo \thechapter}}
 \putinsol{\string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}}
       \@gtempa\endgroup}%
   \def\@wrtail{\xdef\@gtempa{%
 \putinans{\string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}
      \putinans{\putbreak}}
       \@gtempa}
   \def\@wrsoltail{
\xdef\@gtempa{\immediate\write\solutionfile{%
       \string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}
      \immediate\write\solutionfile{\string\pagebreak[3]
         \string\medbreak\noindent}}
       \@gtempa}}% end\bkchap

\def\twocolbkchap{%
  \def\exersection{\section}%
  \def\anstochap{\section}%
  \def\anshead{%
    \addcontentsline{toc}{part}{Answers to selected problems} 
    \chapter*{Answers to selected problems}\label{ansec}
    \chaptermark{}}
  \def\solhead{%
    \chapter*{Solutions to problems\protect\\ 
     not answered in text}
    \chaptermark{}}
   \def\@wrheader{\begingroup
      \xdef\@gtempa{%
 \putinans{\string\anstochap*{Capítulo \thechapter}\string\nopagebreak}
 \putinans{\string\typeout{Soluciones para el Capítulo \thechapter}}
  \putinans{\string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}
%       \putinans{%
% % The following causes the string "Solutions for Chapter n"
% % to be added IN THE FORMAT OF A SECTION ENTRY in the t.o.c
%  \string\addcontentsline{toc}{section}{\string\protect
%  \string\numberline{0}{Solutions for Chapter \thechapter}}}
}
        \@gtempa\endgroup}%
   \def\@wrsolheader{\begingroup
      \xdef\@gtempa%
 {\putinsol{\string\anstochap*{Capítulo \thechapter}\string\nopagebreak}
 \putinsol{\string\typeout{Soluciones para el Capítulo \thechapter}}
 \putinsol{\string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}}
       \@gtempa\endgroup}%
   \def\@wrtail{\xdef\@gtempa{%
 \putinans{\string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}
      \putinans{\putbreak}}
       \@gtempa}
   \def\@wrsoltail{
\xdef\@gtempa{\immediate\write\solutionfile{%
       \string\markboth{Solutions for Chapter \thechapter}
{Solutions for Chapter \thechapter\string\enskip}}
      \immediate\write\solutionfile{\string\pagebreak[3]
         \string\medbreak\noindent}}
       \@gtempa}}% end\bkchap


% Use this command if you are using book style and have at most
% one set of exercises per section.
\def\bksec{%
  \def\exersection{\section}%
  \def\anstochap{\section}%
  \def\ansection{\subsection}%
  \def\anshead{%
    \setcounter{chapter}{-1}
    \setcounter{section}{0}
    \chapter{Answers to selected exercises}\label{ansec}
    \chaptermark{Answers to exercises}}
  \def\solhead{%
    \chapter*{Soluciones para los ejercicios\protect\\ not answered in text}
    \chaptermark{Soluciones para los ejercicios}}
   \def\@nschap{\ifnum \c@chapter >\z@
      {\begingroup
      \xdef\@gtempa{\putinans{%
      \string\typeout{Chapter \thechapter\space solutions}}
% using several \writes keeps the answer file lines from being too long
      \putinans{%
      \string\noindent%
      \string\anstochap*{Solutions for Chapter \thechapter}%
      \string\nopagebreak}
      \putinans{%
 \string\addcontentsline{toc}{chapter}{\string\protect
 \string\numberline{0}{Solutions for Chapter \thechapter}}}}
        \@gtempa\endgroup}\fi}%
   \def\s@lchap{\ifnum \c@chapter >\z@
      {\begingroup
      \xdef\@gtempa{\putinsol{%
      \string\typeout{Chapter \thechapter\space solutions}}
% using several \writes keeps the answer file lines from being too long
      \putinsol{%
      \string\noindent%
      \string\anstochap*{Solutions for Chapter \thechapter}%
      \string\nopagebreak}}%
        \@gtempa\endgroup}\fi}%
   \def\@wrheader{\begingroup
      \xdef\@gtempa{\putinans{%
       \string\ansection*{Secci\'on \thesection}\string\nopagebreak
       \string\markboth{Solutions for section \thesection}
{Solutions for section \thesection\string\enskip}}}
        \@gtempa\endgroup}%
   \def\@wrsolheader{\begingroup
      \xdef\@gtempa{%
 \putinsol{\string\anstochap*{Secci\'on \thesection}\string\nopagebreak}
 \putinsol{\string\typeout{Soluciones de la secci\'on \thesection}}
 \putinsol{\string\markboth{Soluciones para la secci\'on \thesection}
{Soluciones para la secci\'on \thesection\string\enskip}}}
        \@gtempa\endgroup}%
% Following rewrites chapter to write heading in answer section
   \let\ch@@@p=\chapter
   \def\chapter{\ch@@@p\@nschap\s@lchap}
   \def\@wrtail{
\xdef\@gtempa{\putinans{%
       \string\markboth{Solutions for section \thesection}
{Solutions for section \thesection\string\enskip}}
      \putinans{\putbreak}}
    \@gtempa}
   \def\@wrsoltail{
\xdef\@gtempa{\putinsol{\string\markboth{Soluciones para la secci\'on
   \thesection}
{Soluciones para la secci\'on \thesection\string\enskip}}
    \putinsol{\string\pagebreak[3]\string\medbreak\noindent}}
       \@gtempa}}% end\bksec

\def\once{%
  \renewcommand{\exercises}{\setcounter{exercounter}{0}%
     \ifanswerson\answerfalse\subanswerfalse\fi\@wrheader}
  \def\anshead{\relax}
  \def\@wrheader{\putinans{\string\typeout{Answers}}}
   \def\@wrtail{\relax}
  \ifsols{%
\typeout{Sorry, you can't make a Solutions Manual in this style}
\solsfalse}\fi}% end \once

